1. Field of the Invention
The present invention relates to a micromechanical system and a method for manufacturing a micromechanical system.
2. Description of the Related Art
Micromechanical structures (MEMS structures) have manifold uses in the related art, for example, as X and Y acceleration sensors. Such micromechanical systems have a movable element, which is connected via at least one spring element to a substrate. The movable element has electrode fingers, which are adjacent to electrodes connected fixedly to the substrate. An acceleration, which acts on the acceleration sensor, results in a deflection of the movable element, whereby an electrical capacitance between the electrode fingers and the fixed electrodes changes. This capacitance change represents a measure of the magnitude of the acting acceleration.
Applying a thick polysilicon functional layer to a thin buried polysilicon layer on a substrate is known for manufacturing such micromechanical structures. The movable element and the fixed electrodes are manufactured from the functional layer, while the thin layer is used to manufacture printed conductors. In addition, providing a second buried polysilicon layer between the functional layer and the buried polysilicon layer is known from German patent application document DE 102007060878.2.
The fixed electrodes which are manufactured from the functional layer are typically connected in a partial area to the thin polysilicon layer lying underneath. It is desirable to use the thickest possible functional layer, in order to achieve large electrical capacitances. However, the stability of the anchoring of the fixed electrodes decreases with increasing thickness of the functional layer. Excessively large accelerations acting on the micromechanical system could result in breaking off of the fixed electrodes.